The six-foot, 10-inch Isner fired 13 aces in a 7-6 (7-4), 7-6 (7-3) victory over Gulbis in Friday's second men's quarterfinal at this elite hard-court event.

Neither player lost his serve in the first set, which Isner wrapped up in a tiebreaker with one final big serve up the T.

Gulbis struck quickly at the start of the second set by breaking the American's serve at love, but he squandered a chance to serve out the set at 5-4 - netting a backhand on break point - and the players headed to another tiebreaker.

In that "breaker," Isner grabbed a mini-break lead after Gulbis committed a double fault and then wrapped up the contest in one hour and 49 minutes with a backhand down-the-line passing shot.

"Seems like I always have a little bit more adrenaline in those situations, and that was certainly the case out there today," Isner said afterward.

"I certainly hit my biggest serves in those tiebreakers. I think especially the second set one I was going after it with everything I had. They found their mark, too. Helped a lot."

Next up for Isner in Saturday's semifinals will be Djokovic, who found his top form in a 6-1, 6-3 rout of Benneteau in Friday's first men's quarterfinal.

Djokovic, who came up short in January in his bid for a fourth-straight Australian Open title, is still looking to win his first tournament of the 2014 season.

"I came into Indian Wells without a title in this season and that is a different feel from previous years," Djokovic, who lost to Isner two years ago in the Indian Wells semifinals but has a 4-2 lead in their career head-to-head, said after his quarterfinal win.

"I'm on the right path and playing (in the) semifinals, which is always of course a challenge and a good result, but I want to try to go as far as I can."